Modify SQL Question

SELECT Count(1) AS Expr1
FROM (select distinct PatientsID,  iif(datediff('d', End, nz(next_service,End))>30, 1, 0) as MoreThan30 from (
       SELECT P1.PatientsID, P1.EffectiveFrom, P1.End, (select min(EffectiveFrom) from TmpPatBillingCodes as P2 where P2.PatientsID=P1.PatientsID and P2.EffectiveFrom > P1.End) AS next_service
FROM TmpPatBillingCodes AS P1 INNER JOIN Patients3 ON P1.PatientsID = Patients3.ID
WHERE (((Patients3.FacilityID)<>6488) AND ((P1.EffectiveFrom)<#1/1/2014#) AND ((P1.End)>=#1/1/2013#))

) as x
) AS y;